NEW YORK (CBSNewYork/AP) – New York City’s high school class of 2013 is better prepared for college compared to the previous year, according to report cards released Wednesday for 1,624 public schools.

This year’s A-through-F “progress reports” for schools will likely be the last, since Mayor-elect Bill de Blasio has said the formula is too simplistic. The letter grades were ushered in by Mayor Michael Bloomberg in 2007 in an effort to hold schools accountable for student performance.

De Blasio’s spokeswoman Lis Smith said Wednesday that while the mayor-elect supports making information about school progress available to parents, “he would eliminate letter grades of schools which offer little real insight to parents and are not a reliable indicator of how schools are actually performing.”

The grades are based largely on student test scores in comparison to other schools with similar student populations. Elementary and middle schools are graded on a curve, so the approximate number of A’s, B’s and C’s was predetermined. High schools are not graded on a curve.

Eleven schools that were most severely affected by Superstorm Sandy had letter grades withheld, Deputy Schools Chancellor Shael Polakow-Suransky said. Out of the schools that received grades, 27 percent got an A, 36 percent got a B, 28 percent got a C, 6 percent got a D and 3 percent got an F.

The report found that 87 percent of schools maintained their grade or moved one grade compared to last year.

In past years, schools that got bad grades were in danger of being closed. No schools will be threatened with closure this year because of the transition to a new mayoral administration in January.

The college-readiness index is one of the factors used to grade high schools. It is based on whether high school graduates score high enough on SAT or New York state Regents tests to avoid taking remedial classes at a City University of New York campus.

Polakow-Suransky said 31.4 percent of students in the class of 2013 were college ready, compared with 28.6 percent of the class of 2012.

Critics of the school report cards have said the letter grades do not give enough weight to intangible factors like a school’s sense of community.

Polakow-Suransky said the city Department of Education has sought to fine-tune the progress reports so that they can measure schools fairly.

“I think that there are areas of real strength in what we’ve done and there are areas for improvement,” he said. “And one of the big things that we’ve focused on over the past couple of years is how do we get the right balance between the test scores and other qualitative measures.”